In U.S. Pat. No. 4,670,898, entitled `Direct Access Test Unit For Central Office` issued June 2, 1987 by Ben A. Pierce et al and assigned to the assignee of the present application, there is described a test unit that is installed within the equipment frame of a central office which enables a craftsperson or field technician to conduct tests of subscriber lines without the intervention of central office personnel. For this purpose, the patented system is comprised of a processor-controlled interface and test signal generator arrangement that is adapted to be coupled between a line circuit in the central office, through which the craftsperson accesses (calls up) the unit, and a test trunk circuit in the central office through which communications with line circuits associated with the central office are effected. In operation, the craftsperson and the test unit communicate with one another through the tone signalling capability of the craftsperson's handset and voice messages generated by a processor-controlled speech synthesizer circuit within the test unit, the test unit conducting prescribed tests on a specified line circuit in response to tone-keyed test requests from the craftsperson. As a result of these communication and test capabilities of the patented direct access test unit, not only is the need for participation of central office personnel in the testing of subscriber lines circumvented, thereby simplifying trouble-shooting, but the time required to conduct the tests is shortened considerably, which not only saves maintenance costs, but reduces the down time of malfunctioning lines.